Some metal and metalloid polyfluoroaryl compounds are used as activators for polymerization catalysts. Polyfluoroaryl Grignard reagents are useful in the synthesis of tetrakis(polyfluoroaryl)borate salts, from which metal and metalloid polyfluoroaryl compounds are made. When forming tetrakis(polyfluoroaryl)borate salts from a boron trihalide and a polyfluoroaryl Grignard reagent, elevated temperatures are usually needed to drive the reaction to completion (in the sense of adding four groups to boron). However, operating at elevated temperatures causes degradation of the polyfluoroaryl Grignard reagent, which increases the amount of polyfluoroaryl Grignard reagent consumed, thereby increasing production costs.